东海盆地西湖凹陷天台斜坡带平湖组层序格架下沉积差异充填及有利勘探方向  

DIFFERENTIAL DEPOSITIONAL CHARACTERISTICS UNDER SEQUENCE STRATIGRAPHIC FRAMEWORK AND CORRESPONDING EXPLORATION STRATEGIES OF THE PINGHU FORMATION IN TIANTAI SLOPE,XIHU SAG,EAST CHINA SEA BASIN

作　　者：王辉 秦兰芝 李帅 徐东浩 肖晓光 WANG Hui;QIN Lan Zhi;LI Shuai;XU Dong Hao;XIAO Xiao Guang(CNO0C China Limited,Shanghai Branch,Shanghai 200335)

机构地区：[1]中海石油(中国)有限公司上海分公司,上海200335

出　　处：《地层学杂志》2024年第4期419-429,共11页Journal of Stratigraphy

基　　金：十四五中海石油(中国)有限公司重大科技项目4课题2(KJGG2022-0402)资助。

摘　　要：西湖凹陷是东海盆地最为重要的勘探区之一,然而其南部的天台斜坡带由于钻遇井点和取心数量少,对其层序构型和沉积体系的研究比较薄弱,严重制约了后续的勘探工作。本研究通过对天台斜坡带现有的钻井岩心、测井、三维地震及分析测试资料分析,利用层序地层学、地震地貌学、地震沉积学的理论和技术方法,在“四区三段”的地层展布格局下,明确了天台斜坡带平湖组三级层序地层格架及不同断裂体系下的层序发育样式,厘清了构造控制下不同沉积体系的特征及空间展布规律,指出了有利的勘探方向。结果表明:(1)平湖组从下至上可划分出3个三级层序,依次为E2p SQI、E2p SQII和E2pSQⅢ,代表了整体海退背景下的3次大规模海进;受控于断裂发育样式和地貌差异,天台斜坡带可建立3种层序构型,即同向多级顺向窄断阶型、扭动—对向宽缓坡型和伸展—顺向窄缓坡型。(2)天台斜坡带平湖组同时受河流与潮汐影响,发育河控—潮控三角洲,空间上北段—中段潮控作用强、南段弱,时间上自E2p SQⅠ段至E2p SQⅢ段河控作用增强。(3)通过对层序构型控砂模式的研究,天台斜坡带南段发育地层岩性圈闭,中段和北段发育构造—岩性圈闭。The Xihu Sag is one of the most significant exploration areas of the East China Sea Basin.The Tiantai Slope,located in the southwestern part of the Xihu Sag,has long lacked comprehensive studies on depositional patterns and stratigraphic framework due to limited wells and core samples.Based on our integrated analyses of core samples,wireline logs,3D seismic data,and drilling test data in the Tiantai Slope,the third-order sequence stratigraphic framework of the Pinghu Formation(Fm)and the sequence development patterns under various fault systems was established by applying theories of sequence stratigraphy,seismic geomorphology,and seismic sedimentology.In addition,the characteristics and spatial distribution patterns of various sedimentary systems under tectonic controls were unveiled,thereby the next-step exploration strategy in the Tiantai Slope was optimized.Results indicate that:(1)The Pinghu Fm could be divided into three third-order sequences,i.e.,E2pSQⅠ,E2pSQⅡ,and E2pSQⅢin ascending order,representing three critical transgressions in the overall second-order regressive background.Due to the differences in fault and geomorphic patterns,three stratigraphic sequences were established in the Tiantai Slope,namely the multi-level synthetic-faulting narrow-slope type,the shearing-antithetic-faulting wide-gentle-slope type,and the extensional-synthetic-faulting narrow-gentle-slope type.(2)The Tiantai Slope was influenced by both rivers and tides during the deposition of the Pinghu Formation,and thus developed river-dominated and tide-dominated deltas together.In space,tidal influence was stronger in the north-middle segment and weakened in the south segment,while in time,river influence became increasingly significant from E2pSQI to E2pSQⅢ.(3)Through our study of sand distribution,stratigraphic–lithologic traps are developed in the southern Tiantai Slope,while structural–lithologic traps are developed in the middle and northern Tiantai Slope.

关 键 词：天台斜坡带 平湖组 层序地层 沉积特征 

分 类 号：P534.61[天文地球—古生物学与地层学]